nullable: true で cascade Insert したい (typeorm)

前提

node 10.x
typescript 3.5.3
typeorm 0.2.18
mysql 5.7

実現したいこと

typeormで
OneToOne or OneToMany のカラムを nullable: false にする。
その上で cascade Insert, Update したい。

発生している問題・エラーメッセージ

QueryFailedError: ER_BAD_NULL_ERROR: Column 'device_id' cannot be null

該当のソースコード

index.ts

typescript
1// index.ts
2
3import {getRepository} from 'typeorm';
4import {Parent} from '';
5import {Child} from '';
6
7const testCreate = async () => {
8    const parentRepository = getRepository(Parent);
9
10    const parent = new Parent();
11    const child = new Child();
12
13    parent.children = [child];
14
15    await parentRepository.save(parent);
16}
17

child.ts

typescript
1// child.ts
2
3import {
4    Entity,
5    PrimaryGeneratedColumn,
6    Column,
7    BaseEntity,
8    ManyToOne, JoinColumn, CreateDateColumn, UpdateDateColumn } from 'typeorm';
9import { PrimaryGeneratedColumnUUIDOptions } from 'typeorm/decorator/options/PrimaryGeneratedColumnUUIDOptions';
10import { Parent } from './parent';
11
12@Entity('CHILD')
13export class Child extends BaseEntity {
14    @PrimaryGeneratedColumn('uuid')
15    public readonly id?: PrimaryGeneratedColumnUUIDOptions;
16
17    @ManyToOne(
18        (type) => Parent,
19        (parent) => parent.children,
20        { nullable: false },
21    )
22    @JoinColumn({ name: 'parent_id' })
23    public parent!: Parent;
24
25    @CreateDateColumn({ name: 'created_at', type: 'timestamp' })
26    public readonly createdAt?: Date;
27
28    @UpdateDateColumn({ name: 'updated_at', type: 'timestamp' })
29    public readonly updatedAt?: Date;
30
31    constructor(
32        fields: {
33            parent?: Parent,
34        },
35    ) {
36        super();
37        Object.assign(this, fields);
38    }
39
40}

parent.ts

typescript
1import {
2    Entity,
3    PrimaryGeneratedColumn,
4    Column,
5    BaseEntity,
6    OneToMany, CreateDateColumn, UpdateDateColumn } from 'typeorm';
7import { child } from './child';
8
9@Entity('PARENT')
10export class Parent extends BaseEntity {
11    @PrimaryGeneratedColumn({ type: 'bigint' })
12    public readonly id?: number;
13
14    @CreateDateColumn({ name: 'created_at', type: 'timestamp' })
15    public readonly createdAt?: Date;
16
17    @UpdateDateColumn({ name: 'updated_at', type: 'timestamp' })
18    public readonly updatedAt?: Date;
19
20    @OneToMany(
21        (type) => Child,
22        (child) => child.parent,
23        { cascade: true },
24    )
25    public children?: Child[];
26
27}